In our studies of fd coat protein/lipid interactions, we have observed a totally unexpected result: the structure of the coat protein changes radically, from about 50% alpha-helix to about 50% beta-sheet, in response to changes in the lipid/protein ratio and in response to changes in the saturated/unsaturated lipid ratio. Such a lipid-tail group dependence of membrane protein structure has never been reported previously so far as I know. The trhust of the proposed research is to further define and further extend these findings. Specifically we will titrate the alpha-helix to beta-sheet conversion as a function of lipid/protein ratio for different saturated lipids and for different saturated/unsaturated ratios. Laser Raman spectroscopy and circular dichroism will be used to characterize the protein structure. From these studies, we will determine the midpoints of the titration curve and also the widths of the curves. Finally, using these data we will deterine whether temperature can shift the relative amount of the alpha-helix and beta-sheet at a given lipid/protein ratio or at a given saturated/unsaturated ratio. These fundamental studies into the nature of lipid/protein interactions may yield results of considerable importance for the understanding of biological membranes.